Update symmetricDifference

No const
One time new Set()
One line code style

snippets/symmetricDifference.md

@@ -5,11 +5,9 @@ Returns the symmetric difference between two arrays.
 Create a `Set` from each array, then use `Array.filter()` on each of them to only keep values not contained in the other.
 
 ```js
-const symmetricDifference = (a, b) => {
-  const sA = new Set(a),
-    sB = new Set(b);
-  return [...a.filter(x => !sB.has(x)), ...b.filter(x => !sA.has(x))];
-};
+const symmetricDifference = (a, b) => [
+  ...new Set([...a.filter(v => !b.includes(v)), ...b.filter(v => !a.includes(v))])
+];
 ```
 
 ```js